Cytokinesis is a critical process for the reproduction of cells. This process involves the coordinate contraction of an actomyosin ring and organization of the membrane overlying this ring into a discrete membrane domain. Though the actomyosin ring has been extensively studied, the medial membrane has only recently received attention. Through a small genetic screen using fission yeast, our lab has identified an unconventional myosin I involved in the organization of this medial membrane. I propose to characterize the mechanism by which myosin I organizes the medial membrane in fission yeast. I will address the role of interactions between myosin I and the plasma membrane, interactions between myosin I and other proteins, and perform a screen to identify more proteins involved in medial membrane organization. Our model suggests that myosin I organizes the medial membrane by interacting directly with phospholipids on the inner leaflet, and interacting with particular ring components to position the medial membrane. This work will provide an intitial molecular understanding into membrane organization and a model on which to base other systems. [unreadable] [unreadable] [unreadable]